1. Field of the Invention
The present invention relates to a fixing device for fixing an unfixed image on a recording medium.
2. Related Background Art
There are methods in which a recording medium supporting an unfixed image is nipped between and carried by a pair of rotating members to fix the image. Among them, the heating roller method is widely used.
According to the heating roller method, a separation claw which contacts the surface of a fixing roller is generally provided in order to separate the recording medium from the fixing roller.
The surface of the roller is coated with a rubber layer or a resin film in order to improve fixing and separability. But, as the separation claw is pressed against the surface of the roller during rotation, the surface of the roller may be scratched and damaged while frictionally sliding against the separation claw.
In order to solve this problem, the time during which the separation claw is in contact with the surface of the roller may be reduced. Thus, a solution for this problem is to provide a separation claw which can be attached to and detached from the roller, wherein the separation claw remains detached from the roller except when the front edge of the recording medium is to be separated.
However, when the separation claw is detached from the roller after separating the front edge of the recording medium, the retreating separation claw sometimes scratches and disturbs the image. And, when the recording medium is strongly adhered onto the surface of the roller as in case of a solid black image, separation can not be carried out properly.
In addition, as attachment and detachment of the separation claw should be executed for every recording medium, the separation claw has to be operated not only constantly but also swiftly, especially in a high-speed copying machine. Accordingly, the impact which is given when the separation claw comes into contact with the roller causes damage and scratches on the surface of the roller.